1. Field of the Invention
The present invention relates to a network server such as a WWW server for transmitting a hypertext that is written in a language such as HTML or XML, and a transmission control method of a hypertext, and a recording medium storing a hypertext.
2. Description of the Related Art
FIGS. 10A and 10B are diagrams showing a conventional WWW system 9.
Conventionally, a WWW system is widely used as a system for accessing an information resource that is distributed on the Internet.
The WWW system comprises a WWW server for managing the information resource to be provided for a user, a client having a WWW browsing function for accessing thereto, a HTTP placed on a layer upper than the TCP/IP as a communication protocol, and other various devices or software.
The information resource is provided as a hypertext file that is written in a language such as HTML or XML (Extensible Markup Language).
A user inputs and designates a URL of the hypertext that is desired to be accessed in the WWW browser of the client. The WWW browser requests the WWW server to access the hypertext, so as to download the hypertext from the WWW server to the client.
For example, if the HTTP is used as a communication protocol, the URL designating a hypertext “top.html” on a server “WWW.xxxxx.co.jp” is expressed as “http://WWW.xxxxx.co.jp/top.html.”
The WWW system is used not only in the Internet but also in a LAN or an intranet connecting a plurality of LANs.
Many users use the Internet. One object of the Internet is to share information resources among many users in the world. Theoretically, any client on the Internet can access to a hypertext on a WWW server.
However, recent usage of the Internet has become increasingly diversified. There is a need for controlling access to a hypertext so that only specific users are permitted to access.
Some methods are proposed for controlling an access.
One method is establishing a firewall using a proxy server or the like. For example, a firewall is established between an intra-company network and the Internet, so as to control the communication between them. By using the firewall, only specific users are permitted to access the Internet from the intra-company network, or an access using a specific communication protocol is prohibited as an access control.
Another method provides an access control file as shown in FIG. 10B in the directory where the hypertext is placed.
The WWW system 9 shown in FIG. 10A is on the Internet and comprises a WWW server 91 and clients 92 and 93.
The WWW server 91 includes a magnetic recording device 91a, in which a hypertext 91f is recorded as an information resource. The hypertext 91f in the magnetic recording device 91a is managed by a directory structure, and one directory 91d includes an access control file 91c in which information about an access control to the plural hypertexts 91f and the directories 91d thereof is described.
The clients 92 and 93 can access to the Internet by a WWW browser. As an example, the client 92 belongs to a domain “xxxxx.co.jp,” and the client 93 belongs to a domain “zzzzz.co.jp.”
A user inputs a URL of the hypertext 91f in the WWW browser of the client 92 or 93, so as to request for an access to the hypertext 91f. This request is transmitted to the WWW server 91.
The WWW server 91 refers to the access control file 91c that is in the directory 91d where the hypertext 91f is placed and decides whether the hypertext 91f should be transmitted to the client that has made the request.
The access control file 91c shown in FIG. 10B has contents indicating allowing an access from the domain “xxxxx.co.jp” and denying any access from other domains. Therefore, in this case, an access is allowed responding to a request from the client 92, and the hypertext 91f is transmitted to the client 92. On the contrary, an access is denied responding to a request from the client 93, and a message indicating the access denial is transmitted to the client 93.
However, with the above-mentioned access control using the firewall, only an administrator can set the access control and advanced knowledge is required for the setting. If the setting is misused, the security of the entire system can be deteriorated. In addition, it is difficult to set the access control for each file. Therefore, the method using a firewall is not suitable for precise access control.
A method of providing an access control file 91c can control an access for each directory, so it is often used by a service provider of the Internet who provides many users (who open a Web site and offer information resources such as Web contents) with a service. The Internet service provider gives a directory to each information provider. Each information provider stores a hypertext 91f as an information resource in his or her directory, so that many users on the Internet can share the hypertext 91f. 
Since one access control file 91c is placed in one directory 91d, a uniform access control is performed for all hypertexts 91f in the directory 91d. Therefore, if a different setting of the access control is desired for each hypertext 91f, a directory 91d should be provided for each hypertext 91f. 
However, a directory is used for making classification of files be easily understood for an administrator in accordance with kinds or contents of the file. The usage of the directory for the access control may complicate the file management. In addition, if the URL of the hypertext 91f is changed whenever the setting of the access control is changed in the WWW server 91, it may be inconvenient for the user of the client side to access to the hypertext 91f. 
Furthermore, since the access control file 91c depends on software that is used in the WWW server 91 for the access control, it is necessary to understand grammar and rules of the language used in the software for making the access control file 91c. Otherwise, the access control file 91c that is written incorrectly may cause a wrong access control or may deteriorate the security of the entire WWW server 91.
For this reason, many service providers of the Internet prohibit the access control file 91c from being placed on the directory, or use software that ignores the presence of the access control file 91c. 
Therefore, it is difficult to control the access for each information resource by any of the above-mentioned methods.